Rethinking Update-in-Place Key-Value Stores for Modern Storage
Several widely-used key-value stores, like RocksDB, are designed around log-structured merge trees (LSMs). Optimizing for the performance characteristics of HDDs, LSMs provide good write performance by emphasizing sequential access to storage. However, this approach negatively impacts read performan...
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| Format: | Thesis |
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Massachusetts Institute of Technology
2022
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| Online Access: | https://hdl.handle.net/1721.1/144764 https://orcid.org/ 0000-0003-2851-8840 |
| Summary: | Several widely-used key-value stores, like RocksDB, are designed around log-structured merge trees (LSMs). Optimizing for the performance characteristics of HDDs, LSMs provide good write performance by emphasizing sequential access to storage. However, this approach negatively impacts read performance: LSMs must employ expensive compaction jobs and memory-consuming Bloom filters in order to achieve reasonably fast reads. In the era of NVMe SSDs, we argue that this trade-off between read performance and write performance is sub-optimal. With enough parallelism, modern storage media have comparable random and sequential access performance, making update-in-place designs, which traditionally provide high read performance, a viable alternative to LSMs.
In this thesis, based on a research paper currently under submission, we close the gap between log-structured and update-in-place designs on modern SSDs by taking advantage of data and workload patterns. Specifically, we explore three key ideas: (A) record caching for efficient point operations, (B) page grouping for high-performance range scans, and (C) insert forecasting to reduce the reorganization costs of accommodating new records. We evaluate these ideas by implementing them in a prototype update-in-place key-value store called TreeLine. On YCSB, we find that TreeLine outperforms RocksDB and LeanStore by 2.18× and 2.05× respectively on average across the point workloads, and by up to 10.87× and 7.78× overall. |
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